Bar-J Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bar-J Ranch clear sky chart from 2005-11-05 to 2017-05-01.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
42%
15472
28%
45671
13%
15426
56%
15426
42%
23705

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
30%
885
31%
2491
11%
880
50%
880
48%
1212
January16th to endNight
27%
768
35%
2496
15%
768
50%
768
48%
1091
February1st to 15thNight
23%
702
26%
2246
7%
698
44%
698
40%
1108
February16th to endNight
23%
632
37%
1894
7%
632
53%
632
44%
932
March1st to 15thNight
33%
720
29%
2088
11%
720
50%
720
45%
1030
March16th to endNight
34%
694
31%
2038
12%
694
52%
694
40%
1057
April1st to 15thNight
34%
539
26%
1798
12%
539
53%
539
35%
888
April16th to endNight
33%
540
24%
1800
12%
540
52%
540
30%
990
May1st to 15thNight
38%
497
21%
1534
13%
497
49%
497
28%
927
May16th to endNight
47%
514
18%
1370
7%
513
57%
513
38%
800
June1st to 15thNight
56%
495
25%
1320
15%
495
64%
495
50%
681
June16th to endNight
68%
495
23%
1320
18%
495
72%
495
50%
695
July1st to 15thNight
66%
465
17%
1240
15%
465
67%
465
30%
810
July16th to endNight
74%
522
14%
1383
15%
489
75%
489
32%
852
August1st to 15thNight
68%
494
15%
1534
14%
491
69%
491
28%
936
August16th to endNight
70%
525
21%
1750
23%
525
72%
525
32%
997
September1st to 15thNight
65%
495
26%
1650
24%
495
71%
495
32%
942
September16th to endNight
64%
497
34%
1765
28%
497
75%
497
47%
784
October1st to 15thNight
49%
660
32%
1980
18%
660
61%
660
47%
1012
October16th to endNight
49%
704
37%
2112
17%
704
63%
704
49%
1025
November1st to 15thNight
42%
869
36%
2269
15%
869
55%
869
56%
1108
November16th to endNight
35%
900
39%
2385
13%
900
54%
900
56%
1156
December1st to 15thNight
25%
900
28%
2520
5%
900
44%
900
44%
1275
December16th to endNight
26%
960
29%
2688
7%
960
45%
960
42%
1397

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
442442445%8%54%
46092
Night
341332345%7%60%
45851
TransparencyDay
25%5%13%25%22%7%
45775
Night
21%5%14%28%22%6%
45671
SeeingDay
11%15%33%24%12%1
5159
Night
5%9%36%33%13%
15476

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
412323346%66%
1456
16th to endDay
1313312247%66%
1728
February1st to 15thDay
15%25%21335%8%59%
1615
16th to endDay
42432245%7%62%
1580
March1st to 15thDay
2424423348%57%
1869
16th to endDay
26%244345%5%8%51%
2185
April1st to 15thDay
36%344345%48%52%
2150
16th to endDay
8%9%35%4345%5%5%45%
2160
May1st to 15thDay
8%6%36%5%25%6%6%7%40%
2093
16th to endDay
6%5%23435%5%6%8%47%
2392
June1st to 15thDay
4413426%5%7%9%50%
2310
16th to endDay
2213425%5%6%7%55%
2310
July1st to 15thDay
7%425%5%46%6%6%9%43%
2310
16th to endDay
5%6%25%5%47%6%7%9%38%
2371
August1st to 15thDay
7%5%35%5%46%5%6%9%39%
2087
16th to endDay
7%5%244345%7%8%45%
2100
September1st to 15thDay
6%5%25%4245%7%6%48%
1980
16th to endDay
4313322345%65%
1861
October1st to 15thDay
4313314347%62%
1650
16th to endDay
3312213345%66%
1754
November1st to 15thDay
213212247%70%
1583
16th to endDay
213212228%70%
1572
December1st to 15thDay
424212348%63%
1440
16th to endDay
221321245%9%61%
1536
January1st to 15thNight
312222347%68%
2491
16th to endNight
1213212335%71%
2496
February1st to 15thNight
1424312337%63%
2236
16th to endNight
424322346%65%
1894
March1st to 15thNight
141331236%8%62%
2088
16th to endNight
25%24214246%62%
2038
April1st to 15thNight
36%23213347%61%
1798
16th to endNight
9%8%23323346%53%
1800
May1st to 15thNight
10%9%3433345%6%46%
1533
16th to endNight
8%4232245%6%7%52%
1369
June1st to 15thNight
421221345%10%61%
1320
16th to endNight
32221346%8%62%
1320
July1st to 15thNight
8%4246%35%6%7%9%40%
1320
16th to endNight
4325%5%36%7%9%12%40%
1486
August1st to 15thNight
5%315%6%36%5%8%7%45%
1543
16th to endNight
6%424335%5%6%9%45%
1750
September1st to 15thNight
9%5%1443446%9%46%
1650
16th to endNight
4312213346%65%
1765
October1st to 15thNight
4412213445%64%
1980
16th to endNight
441221335%6%65%
2112
November1st to 15thNight
112312347%69%
2269
16th to endNight
1312212346%70%
2385
December1st to 15thNight
324322246%66%
2520
16th to endNight
132432245%7%62%
2688

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
17%314%38%23%2
1457
16th to endDay
18%213%35%24%5%
1728
February1st to 15thDay
20%5%14%36%18%4
1616
16th to endDay
20%310%30%28%6%
1580
March1st to 15thDay
22%311%27%28%6%
1869
16th to endDay
27%6%10%27%23%4
2185
April1st to 15thDay
27%411%28%20%7%
2150
16th to endDay
37%5%9%22%20%5%
2160
May1st to 15thDay
36%8%14%20%17%2
2093
16th to endDay
29%7%16%20%17%7%
2396
June1st to 15thDay
25%6%14%18%22%12%
2310
16th to endDay
21%6%10%19%27%13%
2310
July1st to 15thDay
34%7%14%19%16%8%
2161
16th to endDay
35%8%18%21%12%3
2212
August1st to 15thDay
35%10%14%16%15%6%
2072
16th to endDay
30%6%14%23%18%5%
2100
September1st to 15thDay
29%5%14%21%19%9%
1980
16th to endDay
19%310%24%32%9%
1861
October1st to 15thDay
20%410%24%30%8%
1650
16th to endDay
19%27%28%33%8%
1754
November1st to 15thDay
14%311%25%33%11%
1583
16th to endDay
14%25%35%30%10%
1572
December1st to 15thDay
18%417%34%20%3
1440
16th to endDay
19%5%20%32%17%5%
1536
January1st to 15thNight
16%317%33%25%3
2491
16th to endNight
15%314%33%26%5%
2496
February1st to 15thNight
21%416%36%17%3
2246
16th to endNight
19%210%32%28%6%
1894
March1st to 15thNight
18%413%30%29%4
2088
16th to endNight
21%5%11%31%26%2
2038
April1st to 15thNight
22%5%12%29%22%6%
1798
16th to endNight
31%413%26%18%5%
1800
May1st to 15thNight
36%5%14%21%17%4
1534
16th to endNight
25%8%18%21%17%8%
1370
June1st to 15thNight
17%6%17%24%17%16%
1320
16th to endNight
19%6%13%23%20%16%
1320
July1st to 15thNight
35%9%16%20%10%8%
1240
16th to endNight
30%11%25%20%9%2
1383
August1st to 15thNight
30%12%19%17%13%6%
1534
16th to endNight
29%8%18%26%13%4
1750
September1st to 15thNight
30%7%15%20%15%9%
1650
16th to endNight
18%311%29%29%7%
1765
October1st to 15thNight
20%411%23%29%9%
1980
16th to endNight
18%48%27%33%7%
2112
November1st to 15thNight
14%213%28%29%11%
2269
16th to endNight
14%29%33%32%8%
2385
December1st to 15thNight
19%317%34%22%2
2520
16th to endNight
19%5%19%30%20%3
2688

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
8%14%37%24%14%
90
16th to endDay
7%7%40%38%6%
96
February1st to 15thDay
11%21%44%20%3
90
16th to endDay
8%20%39%18%11%1
81
March1st to 15thDay
15%18%40%20%5%
159
16th to endDay
18%33%36%10%1
288
April1st to 15thDay
14%37%29%13%4
269
16th to endDay
24%35%29%9%1
270
May1st to 15thDay
14%19%38%22%5%
309
16th to endDay
13%13%33%26%12%
437
June1st to 15thDay
8%13%32%28%14%2
420
16th to endDay
39%31%29%21%3
420
July1st to 15thDay
11%6%25%27%25%4
400
16th to endDay
10%323%34%24%3
356
August1st to 15thDay
13%7%34%27%12%3
255
16th to endDay
16%435%28%13%1
268
September1st to 15thDay
9%18%39%24%8%
255
16th to endDay
7%8%37%26%15%4
144
October1st to 15thDay
413%21%38%18%3
90
16th to endDay
8%14%30%23%20%2
96
November1st to 15thDay
48%24%33%23%5%
90
16th to endDay
13%14%45%23%3
90
December1st to 15thDay
8%18%56%14%1
90
16th to endDay
5%20%45%23%31
96
January1st to 15thNight
315%47%25%7%1
885
16th to endNight
213%50%25%6%
768
February1st to 15thNight
5%11%54%26%2
704
16th to endNight
216%53%23%3
632
March1st to 15thNight
415%42%32%6%
720
16th to endNight
6%12%43%32%5%
694
April1st to 15thNight
6%17%36%33%5%
539
16th to endNight
13%12%36%30%7%
540
May1st to 15thNight
14%9%31%35%9%
498
16th to endNight
10%7%28%37%15%
515
June1st to 15thNight
6%427%43%15%1
495
16th to endNight
3219%47%25%
495
July1st to 15thNight
8%19%42%34%2
465
16th to endNight
6%7%38%45%1
522
August1st to 15thNight
7%110%40%37%2
494
16th to endNight
8%19%41%36%3
525
September1st to 15thNight
10%215%45%24%2
495
16th to endNight
6%5%18%44%23%1
497
October1st to 15thNight
5%5%34%38%14%1
660
16th to endNight
6%5%34%37%14%
704
November1st to 15thNight
213%38%34%10%
869
16th to endNight
412%45%31%6%
900
December1st to 15thNight
214%52%25%4
900
16th to endNight
315%50%26%4
960
Page generated at 2017-05-02 06:43:29. Version ac04

Copyright 2017 A. Danko


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